1. Field of the Invention
The present invention relates to a sample holder for holding a sample to be observed in an electron microscope such as a transmission electron microscope, a sample mount on which the sample is affixed, and a sample mount jig for grasping and holding the sample mount.
2. Description of the Background Art
Structural evaluation using an electron microscope has been conventionally employed as one of methods for examining and evaluating semiconductor devices. The electron microscopes mainly include the scanning electron microscopes (SEM) and the transmission electron microscopes (TEM). In the SEM, a beam of electrons is applied to a cleavage plane or an FIB (Focused Ion Beam) processed plane of the sample being observed (observed sample) and secondary electrons etc. obtained from there form an image for observation. In the TEM, a beam of electrons is transmitted through a very thin, 1 xcexcm thick or less, observed sample and transmitted electrons and scattered electrons (elastically scattered electrons) form an image for observation of the internal structure of the sample.
FIGS. 19A and 19B are diagrams showing a generally used conventional TEM sample holder. FIG. 19A is a plane view of the conventional TEM sample holder and FIG. 19B is a front view showing the structure. A sample 105 to be observed, e.g. a semiconductor device, is set on a sample mount 101 provided at an end of the sample holder 100. The observed sample 105 is shaped like a plate having a film thickness of 0.5 xcexcm or less in the direction of incidence of the electron beam (Z direction). The part where the observed sample 105 is set on the sample mount 101 is a pole piece element, which is opened above and below the observed sample 105 (in the Z direction) to allow passage of the electron beam.
The TEM sample holder 100 shown in FIGS. 19A and 19B is a so-called two-axis inclined sample holder which has been conventionally used, where the observed sample 105 can be turned and inclined about axes in the X direction and the Y direction. FIG. 20 shows the observed sample 105 turned and inclined on the axis extending along the X direction (hereinafter referred to as X-axis inclination). In the drawing, the arrow AR20 shows the direction of incidence of the electron beam, i.e. the direction of observation. The X-axis inclination is achieved by a goniometer attached to the body of the TEM; the entirety of the TEM sample holder 100 turns on the axis in the X direction. As the TEM sample holder 100 turns, the sample mount 101 and the observed sample 105 set on it turn and incline, too. In the conventional TEM sample holder 100, the X-axis inclination is possible within a maximum inclination angle of xc2x130xc2x0.
FIG. 21 is a diagram showing the observed sample 105 turned and inclined on the axis extending in the Y direction (hereinafter referred to as Y-axis inclination). The arrow AR21 in the diagram shows the direction of incidence of the electron beam, i.e. the direction of observation. In the Y-axis inclination, a motor provided in the TEM sample holder 100 turns the sample mount 101. As the sample mount 101 turns relative to the TEM sample holder 100 on the axis in the Y direction, the observed sample 105 set on it, too, turns and inclines accordingly. In the conventional sample mount 101, the Y-axis inclination is possible within a maximum inclination angle of xc2x130xc2x0.
Thus, with the conventional two-axis inclined sample holder, the observed sample 105 can be observed from desired directions, e.g. from a particular orientation of the crystal structure, through the X-axis inclination and the Y-axis inclination of the observed sample 105.
The recent remarkable advances in manufacture of the semiconductor devices are achieving finer and more complicated structures and therefore more detailed structural evaluations are needed. It is hence desirable to observe the semiconductor device from a greater number of directions.
However, the conventional X-axis inclination and Y-axis inclination can be made within the limited ranges (e.g. xc2x130xc2x0) and therefore the semiconductor device can be observed only in the limited ranges. It has been hence extremely difficult to observe the semiconductor device in many directions.
The processing by FIB is now attracting particular interests as a technique for forming the thin-film sample 105 from a semiconductor device. The FIB usually uses Ga liquid metal etc. as the ion source; an ion beam focused to several micrometers or less scans the object to sputter-etch a particular area, whereby the area to be observed can be precisely obtained as a thin film. The observed sample 105 formed by the FIB processing is so small that its handling is complicated and difficult. Therefor it will be convenient if the FIB process can be applied to a sample being mounted on a TEM sample holder.
According to a first aspect of the present invention, a sample holder for holding a sample to be observed in an electron microscope comprises: a sample mount on which the sample is affixed; and a rotation driving mechanism for rotating the sample mount about a predetermined axis in the range of 0 to 360xc2x0.
Preferably, according to a second aspect, in the sample holder, the rotation driving mechanism rotates the sample mount in the range of 0 to 360xc2x0 about an axis extending along a direction other than the direction of electron beam incidence in the electron microscope.
Preferably, according to a third aspect, the sample holder further comprises a cartridge portion coupled to the sample mount and a fixed portion coupled to the main body of the sample holder, wherein the cartridge portion can be attached to and removed from the fixed portion.
A fourth aspect is directed to a sample mount jig for grasping and holding a sample mount provided in a sample holder for holding a sample to be observed in an electron microscope. According to the fourth aspect, the sample mount jig comprises: a protecting portion for covering the sample affixed on the sample mount when the sample mount jig is grasping the sample mount; and a grip portion fixed to the protecting portion.
A fifth aspect is directed to a sample mount on which a sample to be observed is affixed and which is provided in a sample holder for holding the sample in an electron microscope. According to the fifth aspect, the sample mount comprises: a mount plate having a gap whose width is narrower than the length of the sample, for supporting the sample affixed thereon, wherein the sample is laid over opposite portions of the gap of the mount plate.
Preferably, according to a sixth aspect, the sample mount is composed of the mount plate and a support plate for supporting the mount plate, the mount plate and the support plate being combined in the shape of L in section.
Preferably, according to a seventh aspect, in the sample mount, the mount plate is in the form of a flat plate.
An eighth aspect is directed to a sample holder for holding a sample to be observed in an electron microscope. According to the eighth aspect, the sample holder comprises: a sample mount composed of a mount plate on which the sample is affixed and supported and a support plate for supporting the mount plate, the mount plate and the support plate being combined in the shape of L in section; and a holding portion for holding the support plate of the sample mount; wherein the mount plate has a gap whose width is narrower than the length of the sample and the sample is laid over opposite portions of the gap of the mount plate.
Preferably, according to a ninth aspect, in the sample holder, the holding portion holds the sample mount in such a manner that the part of the mount plate where the sample is affixed protrudes from the sample holder.
Preferably, according to a tenth aspect, in the sample holder, the holding portion comprises a first holding portion for holding the support plate in such a manner that the normal direction of the mount plate extends along the direction of electron beam incidence in the electron microscope, a second holding portion for holding the support plate in such a manner that the normal direction of the mount plate extends along a first direction which is vertical to the direction of the electron beam incidence, and a third holding portion for holding the support plate in such a manner that the normal direction of the mount plate extends along a second direction which is vertical to both of the direction of the electron beam incidence and the first direction.
Preferably, according to an eleventh aspect, in the sample holder, the holding portion holds the support plate in such a manner that the normal direction of the mount plate extends along the direction of electron beam incidence in the electron microscope or along a first direction which is vertical to the direction of the electron beam incidence and the holding portion can be rotated in the range of 0 to 360xc2x0 about an axis extending along the first direction.
According to the first aspect of the invention, the sample mount is rotated in the range of 0 to 360xc2x0 on a predetermined axis so that the sample can be observed from many directions. It is also possible to FIB-process the sample from many directions without removing the sample from the sample holder, thus facilitating the handling of the sample in the FIB processing.
According to the second aspect, the sample mount is rotated in the range of 0 to 360xc2x0 on an axis extending along a direction other than the direction of the electron beam incidence in the electron microscope, which allows the sample to be certainly observed from many directions.
According to the third aspect, the sample holder has a cartridge portion coupled to the sample mount and a fixed portion coupled to the main body of the sample holder, where the cartridge portion can be attached to and removed from the fixed portion. It is therefore possible to easily replace the sample just by replacing the cartridge portion, thus improving the efficiency of the work.
According to the fourth aspect, the sample mount jig has a protecting portion which covers the sample affixed on the sample mount when the sample mount jig grasps and holds the sample mount. The protecting portion protects the sample from breakage etc. in storage of the sample.
According to the fifth aspect, the sample mount has a gap whose width is narrower than the length of the sample and the sample is positioned across opposite portions over the gap. Hence the electrons transmitted through the sample can pass through the gap to allow observation of the sample from many directions.
According to the sixth aspect, the mount plate on which the sample is affixed and supported and the support plate for supporting the mount plate are combined to form a sectionally L-shaped sample mount and the mount plate has a gap. Accordingly, the sample can be observed from more directions, and also can be handled easily since it can be handled together with the sample mount on which it is affixed.
According to the seventh aspect, the sample mount is formed like a flat plate so as to reduce the influence of scattered electron beam in EDS measurement, so as to improve the measuring accuracy.
According to the eighth aspect, the sample holder has the sample mount of the sixth aspect and a holding portion for holding the support plate of the sample mount, so that the sample can be observed from many directions and handled easily in the FIB processing.
According to the ninth aspect, the sample mount is held by the holding portion so that the part of the mount plate where the sample is affixed protrudes from the sample holder, so that the FIB processing can be easily applied from many directions and the sample can be handled more easily in the FIB processing.
According to the tenth aspect, the sample can be observed from three directions because the holding portion includes a first holding portion for holding the support plate so that the normal direction of the mount plate extends along the direction of electron beam incidence in the electron microscope, a second holding portion for holding the support plate so that the normal direction of the mount plate extends along a first direction which is vertical to the direction of the electron beam incidence, and a third holding portion for holding the support plate so that the normal direction of the mount plate extends in a second direction which is vertical to both of the electron beam incidence direction and the first direction. The sample can thus be observed from many directions and easily handled in the FIB processing.
According to the eleventh aspect, the holding portion holds the support plate so that the normal direction of the mount plate extends along the direction of electron beam incidence in the electron microscope or along a first direction which is vertical to the direction of the electron beam incidence, and the holding portion can be rotated in the range of 0 to 360xc2x0 on an axis along the first direction. Therefore the sample can be observed from more directions and easily handled in the FIB processing.
It is therefore an object of the present invention to provide a sample holder and a sample mount which enable an objective sample to be observed from many directions in an electron microscope.
Another object of the present invention is to provide a sample holder, a sample mount and a jig for use with the sample mount which allow the sample to be handled conveniently.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.